Does Galactic Internet Exists? When Humans Could Be Able To Build Theirs? (Astronomy)

Maccone in his recent paper showed that galactic internet could be made possible by star gravitational lensing and it may already existed

Friends, according to general relativity, all stars are endowed with a powerful focusing effect called “gravitational lensing”. This means that plane electromagnetic waves reaching the proximity of a (spherical) star from a distant radio source are deflected by the star gravity field and made to focus on the opposite side, as shown in Figure 1.

Fig 1: Geometry of the Sun gravitational lens with the minimal focal length of 550 AU (= 3.17 light days = 13.75 times beyond Pluto’s orbit) and the FOCAL spacecraft position beyond the minimal focal length. © Maccone

550 AU ≈ 3.171 light days is the minimal distance from the Sun’s center that the FOCAL spacecraft must reach to get magnified pictures of sources located on the other side of the Sun with respect to the spacecraft position. Also, a simple and important consequence is that all points on the straight line beyond this minimal focal distance are foci too. In fact, the light rays passing by the Sun further than the minimum distance have smaller deflection angles and thus come together at an even greater distance from the Sun. Thus, it is not necessary to stop the FOCAL spacecraft at 550 AU. It can go on to almost any distance beyond and focalize as well or better. The further it goes beyond 550 AU the better it is, since the less distorted are the radio waves by the Sun Corona fluctuations. These are, in short, all FOCAL missions.

Now, Claudio Maccone in his recent paper, disclosed that Galactic Internet is already in existence, if all stars are exploited as gravitational lenses and was created long ago by civilizations more advanced than ours.

Recently, Maccone published two papers in which he mathematically described the “radio bridges” created by the gravitational lens of the Sun and of any nearby star like Alpha Centauri A, or Barnard’s star, or Sirius. The result is that it is indeed possible to communicate between the solar system and a nearby interstellar system with modest signal powers if two FOCAL mission as set up: 1) One by Humans at least at 550 AU from the Sun in the opposite direction to the selected star, and 2) one by ETs at the minimal focal distance of their own star in the direction opposite to the Sun. He showed that civilization much more advanced than Humans in the Galaxy might already have created such a network of cheap interstellar links: a truly GALACTIC INTERNET that Humans will be unable to access as long as they won’t have access to the magnifying power of their own star, the Sun, i.e. until they will be able to reach the minimal focal distance of 550 AU by virtue of their own FOCAL space missions.

Now, he studied another possibility: how to create the future interstellar radio links between the solar system and any future interstellar probe by utilizing the gravitational lens of the Sun as a huge antenna. In particular, he studied the Bit Error Rate (BER) across interstellar distances with and without using the gravitational lens effect of the Sun. The conclusion is that only when we will exploit the Sun as a gravitational lens we will be able to communicate with our own probes (or with nearby Aliens) across the distances of even the nearest stars to us in the Galaxy, and that at a reasonable Bit Error Rate.

He also studied the radio bridge between the Sun and any other Star that is made up by the two gravitational lenses of both the Sun and that Star. The alignment for this radio bridge to work is very strict, but the powersaving is enormous, due to the huge contributions of the two stars’ lenses to the overall antenna gain of the system (shown by me below). For instance, he studied in detail: 1) The Sun–Alpha Cen A radio bridge (2) The Sun–Barnard’s Star radio bridge (3) The Sun–Sirius A radio bridge (4) The radio Bridge between the Sun and any sun–like star located in the Galactic Bulge. (5) The radio Bridge between the Sun and a sun–like star located in the Galactic Bridge. Lets have a closer look on all these radio bridges.

1) The Sun–Alpha Cen A radio bridge

Fig 2 © Maccone

Figure 2 shows the Bit Error Rate (BER) for the double-gravitational-lens system giving the radio bridge between the Sun and Alpha Cen A. In other words, there are two gravitational lenses in the game here: the Sun one and the Alpha Cen A one, and two 12-meter FOCAL spacecrafts are supposed to have been put along the two-star axis on opposite sides at or beyond the minimal focal distances of 550 AU and 749 AU, respectively. This radio bridge has an OVERALL GAIN SO HIGH that a miserable 10¯4 watt transmitting power is sufficient to let the BER get down to zero, i.e. to have perfect telecommunications! Fantastico! Notice also that the scale of the horizontal axis is logarithmic, and the trace is yellowish since the light of Alpha Cen A is yellowish too. This will help us to distinguish this curve from the similar curve for the Barnard’s Star, that is a small red star 6 light years away, as we study next.

2) The Sun – Barnard’s Star radio bridge

Fig 3 © Maccone

Fig. 3 shows the Bit Error Rate (BER) for the double-gravitational-lens of the radio bridge between the Sun and Alpha Cen A (yellowish curve) plus the same curve for the radio bridge between the Sun and Barnard’s star (reddish curve, just as Barnard’s star is a reddish star): for it, 10¯3 watt are needed to keep the BER down to zero, because the gain of Barnard’s star is so small when compared to the Alpha Centauri A’s.

(3) The Sun–Sirius A radio bridge

Fig 4 © Maccone

Fig. 4 shows the Bit Error Rate (BER) for the double-gravitational-lens of the radio bridge between the Sun and Alpha Cen A (yellowish curve) plus the same curve for the radio bridge between the Sun and Barnard’s star (reddish curve, just as Barnard’s star is a reddish star) plus the same curve of the radio bridge between the Sun and Sirius A (blue curve, just as Sirius A is a big blue star). From this blue curve we see that only 10¯4 watt are needed to keep the BER down to zero, because the gain of Sirius A is so big when compared the gain of the Barnard’s star that it “jumps closer to Alpha Cen A’s gain” even if Sirius A is so much further out than the Barnard’s star! In other words, the star’s gain and its size combined matter even more than its distance.

(4) The radio Bridge between the Sun and any sun–like star located in the Galactic Bulge

Fig 5 © Maccone

Fig. 5 shows Bit Error Rate (BER) for the double-gravitational-lens of the radio bridge between the Sun and Alpha Cen A (orangish curve) plus the same curve for the radio bridge between the Sun and Barnard’s star (reddish curve, just as Barnard’s star is a reddish star) plus the same curve of the radio bridge between the Sun and Sirius A (blue curve, just as Sirius A is a big blue star). In addition, to the far right we now have the pink curve showing the BER for a radio bridge between the Sun and another Sun (identical in mass and size) located inside the Galactic Bulge at a distance of 26,000 light years. The radio bridge between these two Suns works and their two gravitational lenses works perfectly (i.e. BER = 0) if the transmitted power is higher than about 1000 watts.

(5) The radio Bridge between the Sun and a sun–like star located in the Galactic Bridge

Fig 6 © Maccone et al.

Fig. 6 shows the four Bit Error Rate (BER) curves plus the new cyan curve appearing here on the far right: this is the BER curve of the radio bridge between the Sun and another Sun just the same but located somewhere in the Andromeda Galaxy M 31. Notice that this radio bridge would work fine (i.e. with BER = 0) if the transmitting power was at least 107 watt = 10 Megawatt. This is not as “crazy” at it might seem if one remembers that recently the discovery of the first extrasolar planet in the Andromeda Galaxy was announced, and the method used for the detection was just GRAVITATIONAL LENSING !

Finally, he found the information channel capacity for each of the above radio bridges (shown in table 1), putting thus a physical constraint to the amount of information transfer that will be possible even by exploiting the stars as gravitational lenses.

Table 1. Channel Capacities for all five information channels made up by the radio bridges between the Sun and another star. The second and third column give the Channel Capacity for bandwidth equal to 1 Hz (typical SETI case) and 1 kHz (sometimes used in SETI also), respectively. © Maccone

Thus, author reached on conclusions:

(1) A Galactic Internet constructed by advanced Aliens by exploiting the gravitational lenses of stars may already exist in the Galaxy.

(2) The Channel Capacity for each radio bridge between any couple of communicating stars has an upper physical limit (in bits/sec), given by

{1/ln(2)} × {P_r/k_b × T_r),

where, ‘_’ is base, P_r is the received signal power, T_r is the noise temperature of the receiving antenna (radiotelescope) and k_b is Boltzmann’s constant.

3) This Galactic Internet is currently inaccessible to Humans since Humans have not yet reached the minimal focal sphere of the Sun at 550 AU (and beyond, to, say, 1000 AU) by virtue of suitable FOCAL spacecrafts.

4) Even after the focal sphere of the Sun at 550 AU will have been reached by FOCAL spacecrafts, these must be aligned with the star sending the ET signals towards the Sun. Thus, the construction of some sort of “Dyson sphere for telecommunications” around the Sun at 550 AU by future, more advanced Humans might be advisable to put us in touch with the rest of the Galaxy for the first time.


Reference: Claudio Maccone, “Galactic internet made possible by star gravitational lensing”, ArXiv, pp. 1-6, 2021. https://arxiv.org/abs/2103.11483


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